A preliminary analysis of human impacts on sediment discharges from the Yangtze, China, into the sea

Sediment discharge from the Yangtze into the sea has decreased rapidly from 481.7 X 10(6) tons/y (1953-76) to 389.5 X 10(6) tons/y (1977-2000), without any corresponding decrease in water discharge. In 2001, the sediment discharge from the Yangtze dropped to 276 X 106 tons. Human activities and climate changes obviously play a major role for reducing the sediment supply from the upper basin and for increasing the sediment sinks in the mid lower basin. Sediment budgets in different parts of the Yangtze are estimated according to hydrometric data and other sources. Major physical and anthropogenic processes are examined with respect to their effects on sediment discharge from the Yangtze into the sea. The decrease of sediment, supply (-46.8 X 10(6) tons/y) from the upper Yangtze in the second period accounts for about 50% of the total decrease (-92.2 X 106 tons/y) into the sea, mostly due to he increased sedimentation in reservoirs as well as climatic factors. The other 50% decrease is mostly attributed to increased sand mining in the mid-lower Yangtze and the decreased sediment supply from the Hanjiang River after building the Danjiangkou Reservoir.